1. Field of the Invention
The present invention is generally concerned with fixing clamps for attaching an article of any kind to a support of any kind, whether the fixing clamp is permanently fixed to the article, of which it forms an integral part, or constitutes an accessory which is attached to the article only as and when required.
It is more particularly, although not necessarily exclusively, directed to the situation in which the article concerned is an inspection lamp, i.e. a mobile electrical lamp that a user can move as required to illuminate as well as possible a site in which the user is working.
2. Description of the Prior Art
To leave their hands free, it is important for the user to be able to put the inspection lamp down on, and preferably attach it to, a support of any kind, often of an improvised kind.
The fixing clamps commonly provided for this purpose usually have two jaws, both of which pivot, and which are therefore mobile relative to each other between an open position and a closed position, return spring means which spring-load the jaws towards their closed position, and an operating handle, generally a simple lever, for actuating the device which is accessible to the user and which is attached to one of the jaws, referred to hereinafter for convenience only as the bottom jaw, the other jaw being referred to hereinafter for convenience only as the top jaw.
Until now, and for simplicity, the two jaws have been directly articulated to each other about a common rotation axis.
This arrangement has been satisfactory and may continue to be so.
However, it has the drawback that it makes it difficult to meet the usual requirements in a convenient way.
One of these requirements is that, in the closed position of the jaws, the return spring means operating on the jaws must be non-negligibly prestressed.
It is important for the clamping force exerted by the jaws when they are engaged with a support to remain sufficient even if the support is relatively thin, for example a sheet of metal or glass or a ladder rung.
Another requirement is that the angle to which the jaws open must be sufficient, in practise at least 50.degree., so that they can be engaged with a relatively thick support, for example a plank.
Because the two jaws are articulated to each other and because the operating lever is coupled to the bottom jaw, all of the angle to which the jaws can open is reflected in the opening travel of the operating lever, which can make it difficult to handle for at least some users.
Because the force to be exerted on the operating lever inevitably increases as the jaws open, the force is frequently relatively high at the end of travel, which is uncomfortable for the user, if it originally has a non-negligible value to satisfy the aforementioned prestressing requirement, which from this point of view means that the two requirements to be satisfied are contradictory.
A general object of the present invention is an arrangement which overcomes the above problems and has other advantages.